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Since the birth of computer equipment, the keyboard and mouse have been the most basic input devices in the development of human-computer interaction, while the screen is only the output device of computer information.But from beginning to end, the human has been represented by touch technology of natural user interface (commonly known as the touch interface) with longing, because in this operating mode, the people will have the most intuitive feelings and experience, in this kind of operation mode, the screen is not only the output devices, and input devices, can be directly on the screen by touching operations, to control the computer.

With popular consumer digital products such as mobile phones, small screen multi-touch technology mature gradually, at the same time, for the big screen multi-touch technology also gradually become the focus of the commercial display user demand, because relying on multi-touch technology, can realize the interaction with large screen, feelings, experience, can complete the large-scale multimedia interactive, effects demo, and many other wonderful effect, bring more convenient for the daily work and study.

At present, for large-screen commercial display, the realization of large-screen multi-touch technology has been relying on the backscatter infrared light illumination multi-touch technology for several years. The technical principle of backscatter infrared light multi-touch technology is as follows:Infrared light from the back light in a piece of integrated effect of diffuse (the role of the diffuse reflection is to generate a diffuse infrared irradiation on diffuse curtain, reduce read by the camera is reflected the infrared light) on the large screen, when fingers touching the screen, the finger will more infrared reflectance diffuse screen, read by the infrared camera and infrared light is reflected, the formation of electrical signals, finally the related calculation software applications, form a specific touch coordinates, feedback form the screen.

In summary, backscatter light multi-touch technology relies on infrared camera to detect the reflected infrared light of the touch object, so as to locate the touch position.Therefore, from a technical perspective, this technology not only supports the daily finger touch, but also supports the remote air-separation operation of the hand-held infrared laser pen.

However, based on this, if the indoor irradiation or direct sunlight is particularly intense during normal use, excessive infrared light will be detected by the infrared camera, resulting in the system's misjudgment of touch control function, which will seriously interfere and affect the touch control effect of the large screen.

For example, a few years ago, at a ministries in Beijing on a big screen manufacturers design and construction of a piece with a big screen multi-touch function program, time, in the inspection of the ministries and the central leadership, and watch the multi-touch screen demonstration, due to a large number of accompanying reporters intensive flash photos, resulting in live demonstration, appear larger touch failure phenomenon, so as to give the ministries of reception work left a lot of regret.

In fact, from the analysis on technical principles can know: the camera flash instantaneous emit light, not only contains many of the visible light viewable to the human eye, at the same time, the flash will be issued between 200 nm to 400 nm wavelength ultraviolet and infrared light between 700 nm to 1200 nm, and flash a short moment of infrared rays through the screen, by multi-touch infrared camera, and ultimately converted to electrical signals and touch reception these signals clashed with hands touch the touch signal, thus eventually touch screen failure phenomena of chaos.

Now, big screen business show laser screen multi-touch function, USES a laser plane multi-touch technology to realize, its technical principle, respectively at the edge of the screen up and down, left and right sides of a set of laser tube and receiving tube, the woven tubes launch laser grid covered the entire screen surface to form a laser surface, when the finger touching the screen, finger destroyed the screen surface of the vertical and horizontal laser receiving;Therefore, when the receiving lamp does not receive the laser signal, relevant software can find out the specific coordinates of the finger touch position by analyzing the position of the lamp that does not receive the laser signal, and finally guide the screen screen to react according to the finger move position, forming the touch interaction effect.

The biggest technical difference between laser planar multi-touch control and backscatter infrared light multi-touch control is that one is to determine the finger-touch position coordinates according to the position of the laser lamp which has not received the laser, and the other is to determine the finger-touch position coordinates by detecting the infrared ray reflected from the finger-touch position.Therefore, when the external light is strong, the backscatter light multi-touch is more likely to be affected by the interference of invisible infrared light in the external strong light.

At the same time, in the big data and the Internet of things application under the time background of the deepening, more and more scenario requires the use of large size, large areas of commercial display screen, and the biggest laser plane multi-touch technology in the 322 - inch multi-touch screen, realize the people at the same time to smooth touch screen operation, at the same time, relying on the unique intelligent recognition technology, a touch can be implemented on a big screen easily implement complex drawing and writing;The backscatter infrared light multi-touch control is applied to large-size commercial display screen. In many cases, the screen resolution is not up to the screen resolution due to the uneven infrared light projection, which is easy to cause the phenomenon of unpracticed and even disconnection of the lines when the touch is written, which greatly affects the touch control experience.

Finally, at present, the laser plane multi-touch technology has realized the integrated frame structure design and convenient and simple USB power supply, which is more convenient and easy in construction, installation, debugging and later maintenance than the independent design of multi-part of backscatter infrared light multi-touch control.

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